The present invention relates to an improved sleeve valve adapted to control the flow and pressure of fluid such as water in any pipeline section for the fluid.
Prior art flow and pressure control valves for fluid such as water are exemplified by sluice and butterfly valves. However, these sluice and butterfly valves each have the drawback that they can not attain an excellent flow and pressure control because the configuration of fluid flow changes with the extent of the valve opening, and more particularly that it developes the so-called cavitation over its valve opening range less than about 30% because it has a relatively high cavitation index (see FIG. 6), producing a relatively large noise and vibration.
Under these circumstances, a sleeve valve of the hereinunder described construction has been recently developed by the U.S. Bureau of Reclamation. Namely, the sleeve valve comprises a fixed sleeve which has a cylindrical hollow shape with its lower end closed and in the peripheral wall of which a plurality of small taper holes with mutually equal diameters made gradually smaller from its inner wall toward its outer wall are spirally perforated at a substantially equal pitch interval, the fixed sleeve having its open upper end coaxially joined, in a deenergizing tank or tub having its upper wall to which the end of a fluid inflow pipe forming a fluid inlet port for the tank is vertically joined and provided at its predetermined side wall portion with a fluid outflow or overflow aperture, to the end of said fluid inflow pipe; and a movable sleeve engaged with the fixed sleeve so as slidably to move along the inner wall thereof in the upper and lower directions.
The sleeve valve of the above-mentioned construction has its advantage enabling its cavitation index (see FIG. 6) to be set at a smaller value than those of the aforesaid sluice and butterfly valves and consequently preventing cavitation from being produced over its valve opening range more than about 10%, because the configuration of fluid flow is always kept in a circular form without change.
However, the above-mentioned prior art sleeve valve has drawbacks as hereinunder enumerated:
(1) It still produces cavitation over its valve opening range less than about 10%; and
(2) When it is disposed in a fluid pipeline section adjacent to the headwaters such as a dam where the coefficient of pipe loss is almost zero, then it can control to obtain its fluid flow rate substantially proportional to the extent of the moving stroke of the movable sleeve over the whole of the moving stroke thereof, but, when it is installed in a fluid pipeline section considerably remote from the headwaters where the coefficient of pipe loss has a considerably large value, then the greater amount of the whole of the fluid flow to be controlled by the sleeve valve passes therethrough in a considerably smaller valve opening position and consequently the amount of fluid flow to be passed therethrough almost does not change over the large remaining valve opening range (see FIG. 9).
It is therefore the object of the invention to provide a novel sleeve valve enabling its cavitation index at its initial valve opening portion to be set at a smaller value than that of the prior art sleeve valve, and capable of attaining the most excellent possible flow control over the whole of the valve opening range even if it is disposed in a pipeline section where the coefficient of pipe loss has a considerably large value.